Friction Questions and Answers

ation 11 60 BOTANY 165 23 12 17 18 24 29 30 Acceleration of the block A as shown in the figure will be all surfaces are smooth F 100 N massless rod A2 kg 153 OPTIONS MARK FOR REVIEW CLEAR SELECTION A 30 2 m s B 30 m s 24 C 60 m s

a on two inclined plane as shown in the figure 45 smooth 1 1 2 2 3 1 5 4 0 8 K 28 45 Ma rough 0 5 TT The ratio of the accelerations a ag is NCERT I XI Pg 102 Thinking in Context 3 Suppose we are standing in a stationary bus and th

2 6 Two blocks of mass 2 kg and 3 kg are kept on level ground having coefficient of static friction 0 3 and 0 4 respectively from ground The blocks are connected by a spring of constant 100 N m What can be a possible extension in the spring so that both the blocks are in equilibrium g 10ms 2 6 cm 4 15 cm 1 3 cm 3 9 cm

Two equal electric currents are flowing perpendicular to each other as shown in the figure AB and CD are perpendicular to each other and symmetrically placed with respect to the current flow Where do we expect the resultant magnetic field to be zero B A on AB B on CD D I C on both AB and CD D on both OD and BO

22 The co efficient of friction between a chain a table is m If a chain is placed on a horizontal table so that a part of it is hanging from one end The minimum fraction of length of the chain that can be on the table so that the chain may not slip off is

30 A block of mass m is placed on the top of another block of mass M as shown in figure The co efficient of friction between them is the maximum acceleration with which the block M may move so that m also moves along with it is m M a

20 The distance travelled by a body before coming to rest if it is moving on a rough surface with a velocity 18kmph and the coeffcient of friction between the body and the surface is 0 4 is g 10m s Ans 25 8 m

A body of mass m slides down a smooth inclined plane having an inclination of 45 with the horizontal It takes 2s to reach the bottom If the body is placed on a similar plane having co efficient of friction 0 5 What is the time taken for it to reach the bottom

N 4 mg Since the floor is rough it exerts both a normal force N and a frictional force f on the ladder However since the wall frictionless it exerts only a normal force N on the ladder The ladder has a length of L 4 1 m a weight of W 55 0 and rests against the wall a distance d 3 75 m above the floor If a person with a mass of m 90 kg is standing on th ladder determine the following N N N a the forces exerted on the ladder when the person is halfway up the ladder Enter the magnitude only N N N N N b the forces exerted on the ladder when the person is three fourths of the way up the ladder Enter the magnitude only N N

Boxes A and B are sliding to the right across a frictionless table The hand His slowing them down The mass of A is larger than the mass of B Here Fon B represents force on B due to A and same for other A m mB A B Slowing FB on A A on B A FB on H FH on B F C FB on H FH on B FA on B FB on A H Frictionless surface mmm FB B FB on H FH on BFA on B FB on A D FB on H FH on BFA on BFB on A

A force is F is applied circular disc of mass mand radius R which is kept on a smooth surface as shown in the figure The angular acceleration of the body about the x c I centre of mass 2 FRX2 MRZ 1 F mR 2 F 2mR 2F MR

The front wall of a drawer in a cabinet is provider with two symmetrical handles The distance between the handles is and the length i e depth of the drawer is a The maximum value of coefficient of friction between drawer and cabinet for which drawer can be pulled out by applying force on one handle perpendicular to the face of drawer is Neglect the weight of the drawer A 2a B 2 a C 20

The velocity time graph of a body is as shown in the graph 1 State the kind of motion represented by OA and AB 2 What is the velocity of the body after 10 s and after 30 s 3 Calculate retardation of the body 4 Calculate the distance covered by the body between 10th and 30th second Velocity in ms E 10 20 Time in s B D 30

12 In rear wheel drive cars the engine rotates the rear wheels and the front wheels rotate only because the car moves If such a car accelerates on a horizontal road the friction one light on the rear wheels is in the forward direction b on the front wheels is in the backward direction on the rear wheels has larger magnitude than the friction on the front wheels d on the car is in the backward direction F

Question No 17 A Maximum Mark 4 00 Negative Mark 1 00 A block of mass 5 kg is pressed against a wall with a horizontal force of 100 N If the coefficient of friction between the surfaces is 0 8 Then frictional force acting on the block is D 80 N 50 N 20 N 30 N

The coefficient of friction between 12 kg block and 3 kg platform BD are us 0 60 and 0 40 respectively Determine the magnitude of Hk acceleration of the block immediately after the wire AB is cut A 5 m s B 8 m s C 2 5 m s D None of these AB 301 C 12 kg 3 kg D 30

Block A of mass 35 kg is resting on a frictionless floor Another block B of mass 7 kg is resting on it as shown in the figure The coefficient of friction between the blocks is 0 5 while kinetic friction is 0 4 If a force of 100 N is applied to block B the acceleration of the block A will be g 10 ms F 1 0 8 ms 3 0 4 m s 7 kg B 35 kg A 2 2 4 ms 2 4 4 4 m s

A 20 kg block is initially at rest A 75 N force is required to set the block in motion After the motion a force of 60 N is applied to keep the block moving with constant speed The coefficient of static friction is Question Type Single Correct Type 1 0 6 2 0 52 3 0 44

Consider a uniform cubical box of side a on a rough floor that is to be moved by applying minimum possible force F at a point b above its centre of mass see figure If the coefficient of friction is 0 4 the maximum possible b value of 100 x for a box not to topple before a

The following figure shows a logic gate circuit or with two inputs A and B and the output C The voltage waveforms of A B and C are as shown below ODS4 1 A 1 B A mondo Logic gate circuit B 7 C v t L 7 Li t C The logic circuit gate is a NAND gate c OR gate b NOR gate d AND gate 2006

2 The normal force between a snowmobile and the snow has a magnitude of 2200 N the horizontal force needed to get the snowmobile to just start moving has a magnitude of 140 N a Draw a FBD of the snowmobile Be sure to label your forces appropriately and to include values b Calculate the coefficient of static friction in this case

Q 18 SINGLE CHOICE A block A of mass 10 kg is placed on rough horizontal plank B x y plane where gravity act vertically downward Hs 1 2 k 1 All units are in SI Force acting on block A is due to plank B and earth only For the situation in List I match the appropriate description in List II 10 B S a B 13th Z F B mg P Q List I aft 1 VA 31 VB 31 43 a B 31 43 8 VA VB 31 43 a B 8i 63 VA VB 43 A t af d i hefur s as 1 2 k 1 e R affay R a B 81 6k S 8i 6k E Codes cnt3 1 1 2 VA VB 0 a B 4 a List II 11 ART Direction of friction on A is ve y direction 3 A farm Direction of friction on A is ve X direction P 2 Q 5 R 2 S 4 Direction of acceleration of A is ve y direction ARUT PR B P 3 Q 4 5 R 2 S3 A a B P 3 Q 4 5 R 2 S 1 4 Friction force on A is neither in x direction nor in y direction but 5 somewhere in between my fan

A vertical capillary tube with inside radius 0 25 mm is submerged into water so that the length of its part protruding over the water surface is equal to 25 mm Surface tension of water is 73 x 10 N m and angle of contact is zero degree for glass and water acceleration due to gravity is 9 8m s Then value of 10R approximately in mm is where R is radius of meniscus and his height of water in capillary tube

A massless spool of inner radius r outer radius R is placed against a vertical wall and a tilted split floor as shown A light inextensible thread is tightly wound around the spool through which a mass m is hanging There exists no friction at point A while the coefficient of friction between the spool and point B is The angle between the two surfaces is p g R r C A B

Pam s family clearing some land and there is a large bouider ating on top of the ground Even with the entire family pushing on it they cannot move it Which type of friction exists between the boulder and the ground fluid oling ding

d zero 22 The angular velocity of the engine and hence of t wheel of a scooter is proportional to the petrol inp per second The scooter is moving on a frictionless ro with uniform velocity If the petrol input is increased wheel

A block of mass 20 kg is moved with constant velocity along an inclined plane of inclination 37 with help of a force of constant power 50 W If the coefficient of kinetic friction between block and surface is 0 25 then what fraction of power is used against gravity 1 3 4 2 1 4 3 2 4 10

A block of mass 1 kg is connected to a spring of spring constant N m fixed at other end and kept on smooth level ground The block is pulled by a distance of 1 cm from natural length position and released After what time does the block compress the spring by cm

In the situation shown in figure for what value of force F in Newton sliding between middle and low block will start Take g 10 m s fagur ei T C Pay fad GR g 10 m s 0 1 0 6 0 2 2kg 2kg 4kg F

a Frictional force between block and contact surface depends on area of contact b Frictional force may also act when there is no relative motion between the contact surfaces The correct statement is 1 a only 2 b only

A block of mass 4 kg is placed on rough horizontal surface with coefficient of friction 0 5 A time dependent force F 4 9 t acts on block At what time from the instant of applied force the block just tends to move on surface g 9 8 m s 1 s 2 s 3 s

35 A body is moving up an inclined plane of angle 0 with an initial kinetic energy E The coefficient of friction between the plane and body is u The work done against friction before the body comes to rest is E cos 0 a b E c cose sine E cos 0 u cos 0 sin 8 d E cos 0 cos 0 sine

14 A block of mass m slides down a rough inclined plane of inclination with horizontal with zero initial velocity The coefficient of friction between the block and the plane is u with 0 tan u Rate of work done by the force of friction at time tis a mg2 tsine b mg2 t sine cos 0 c mg2 t cos 0 sin 0 cos 0 d mg2t cose

9 A block of mass m is attached with a massless spring of force constant k The block is placed over a rough inclined surface for which the coefficient of 3 The 4 friction is m 3 a m b m 37 ooooo minimum value of M required to move the block up the plane is Neglect mass of string mass of pulley and friction in pulley M 6 udo 3 c msm d m

Two roommates are trying to get an armchair into their apartment They found the armchair did not fit through the front door so they decide to take it below their patio One of them is pulling straight upwards with 250 N of force The other has pressed the armchair against a vertical wall with a force directed upwards at an angle of 30 with respect to the horizontal as shown That pushing force has a total magnitude of 300 N If the armchair is 34 kg and it is sliding up the wall with an acceleration of 0 5 m s what is the coefficient of kinetic friction between the chair and the wall

Consider a system of infinite pulleys and blocks as shown Every next block is twice heavier than the previous one All pulleys and strings involved are ideal System is released from rest If the acceleration of block of mass m is found to be 9 where g is acceleration due to gravity and a B are integers and there B is no common factor in a and B Find a B farger and ford for a a ns 7 RA RA ta quis an an 9 m 2m 18m 30 31 ag B

If a Towing force P of 5 N is applied to keep a body in equilibrium on a plane inclined at and angle of 30degree the weight of body is given as O a 4 3 N O b 5 7 N O c 2 5 N O d 10 N

A block of mass m rests on a rough inclined plane making an angle 30 with the horizontal The coefficient of static friction between the block and the plane is 0 8 If force of friction on the block is 10 N the mass of the block is g 10m s

dt V m A 4 kg slab rests on frictionless floor as shown in Fig 1 17 A 1 kg block rests on the top of the slab The static coefficient of friction between the block and the slab is 0 6 while the kinetic coefficient of friction is 0 4 A horizontal force 10 N acts upon 1Kg block The acceleration of the slab is a 0 98 m s c 1 52 m s Ans a m b 1 47 m s d 6 10 m s 10N SMOOTH LAB Fig 1 17 BLOCK by a massless spring of natural length L and spring

If coefficient of friction between all surfaces is 0 4 then find the minimum force F to have equilibrium of the system Take g 10 m s 62 5 N Wall c 135 N 25 kg bol 15 kg LYON let g a b 150 N d 50 N the arrangement shown in figure there is a friction force between the blocks of masses m and

An object of mass m held against a vertical wall by applying horizontal force F as shown in the figure The minimum value of the force F is F Wall m 1 Less than mg 2 Equal to mg 3 Greater than mg 4 Cannot determine

Given MA 30 kg mB 10 kg mc 20 kg Between A and B 0 3 between B and C 0 2 and between C and ground 3 0 1 The least horizontal force which can start the motion of any part of the system of three blocks resting upon one another as shown in figure is F Write the value of F 12 g 10 m s

A block of weight 200 N is at rest on a rough inclined plane of inclination angle 8 30 The inclined plane is at rest in the earth s inertial frame Then the magnitude of the force the plane exerts on the block is A 100 3 N B 100 N C 200 N D zero

Which of the following is correct when a person walks on a rough surface Ja uch with geak your dadi a A The frictional force exerted by the surface keeps him moving B The force which the man exerts on the floor keeps him moving e The reaction of the force which the man exerts on floor keeps him moving D None of the above

No 24 View In English A cylinder rolls up an inclined plane reaches some height and then rolls down without slipping throughout these motions The directions of the frictional force acting on the cylinder are 1 D 2 4 Correct Answer 2 Your Answer 1 Status incorrect Up the incline while ascending and down the incline while descending Up the incline while ascending as well as descending Down the incline while ascending and up the incline while descending Down the incline while ascending as well as descending

40 A block is released on the slant face of a wedge of equal mass placed on a horizontal floor The slant face of the wedge makes an angle of 45 with the floor Coefficient of friction between all surfaces in contact is the same Find range of coefficient of friction for the following cases a Both the bodies remain motionless TITL the blook alidon down Newton s Laws of Motion 2 21

3 24 A hemispherical bowl of radius R is rotated about its vertical axis A small particle is kept on its inner surface where the radius makes an angle 0 with the vertical The particle rotates with the bowl without any slipping The friction coefficient between the block and the bowl surface is u Find the range of the angular speed for which the block will not slip Ans g sin 0 cos0 Rsin 0 cos0 usin0 1 2 to g sin 0 ucose 7 2 1 Rsin 0 cose usine

Consider two blocks connected as shown in Figure 1 Block A has mass 2 00 kg and block B has mass 5 00 kg The table on which B sits is frictionless the cord connecting the blocks is light and flexible and the pulley is light and frictionless The horizontal force F has magnitude F 19 0 N and block B moves to the left with an acceleration of 1 80 m s Part A What is the tension in the cord that connects the two blocks Express your answer with the appropriate units T Value Submit Part B Jak HA Submit Provide Feedback 1 Request Answer VALO AE What is the coefficient of kinetic friction that one block exerts on the other Request Answer C Units 4

The front wall of a drawer in a cabinet is a provider with two symmetrical handles The distance between the handles is 1 and the length i e depth of the drawer is a The maximum value of the coefficient of friction between drawer and cabinet for which drawer can be pulled out by applying a force on one handle perpendicular to the face of the drawer is Neglect the weight of the drawer

A contestant in a winter games event pushes a 55 0 kg block of ice across a frozen lake as shown in the figure 25 The coefficient of static friction is 0 1 and the coefficient of kinetic friction is 0 03 a Calculate the minirnum force F in N he must exert to get the block moving N b What is its acceleration in m s2 once it starts to move if that force is maintained m s